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68 lines
1.6 KiB
C++
68 lines
1.6 KiB
C++
// (C) Copyright Jeremy Siek 2000. Permission to copy, use, modify, sell and
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// distribute this software is granted provided this copyright notice appears
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// in all copies. This software is provided "as is" without express or implied
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// warranty, and with no claim as to its suitability for any purpose.
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// The ct_if implementation that avoids partial specialization is
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// based on the IF class by Ulrich W. Eisenecker and Krzysztof
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// Czarnecki.
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#ifndef BOOST_CT_IF_HPP
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#define BOOST_CT_IF_HPP
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#include <boost/config.hpp>
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namespace boost {
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#ifndef BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION
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template <int cond, class A, class B>
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struct ct_if { typedef A type; };
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template <class A, class B>
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struct ct_if<0, A, B> { typedef B type; };
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#else
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namespace detail {
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template <int condition, class A, class B> struct IF;
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template <int condition> struct SlectSelector;
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struct SelectFirstType;
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struct SelectSecondType;
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struct SelectFirstType {
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template<class A, class B>
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struct Template { typedef A type; };
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};
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struct SelectSecondType {
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template<class A, class B>
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struct Template { typedef B type; };
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};
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template<int condition>
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struct SlectSelector {
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typedef SelectFirstType type;
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};
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template <>
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struct SlectSelector<0> {
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typedef SelectSecondType type;
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};
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} // namespace detail
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template<int condition, class A, class B>
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struct ct_if
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{
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typedef typename detail::SlectSelector<condition>::type Selector;
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typedef typename Selector::template Template<A, B>::type type;
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};
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#endif
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} // namespace boost
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#endif // BOOST_CT_IF_HPP
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